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Q&A: A lost interview with ENIAC co-inventor J. Presper Eckert

On the the 60th anniversary of the unveiling of ENIAC, a newly discovered interview with "Pres" Eckert explodes some ENIAC myths.

By Alexander Randall 5th
February 14, 2006 12:00 PM ET

Computerworld -

J. Presper Eckert
J. Presper Eckert
There are two epochs in computer history: Before ENIAC and After ENIAC. The first practical, all-electronic computer was unveiled on Feb. 14, 1946, at the University of Pennsylvania's Moore School of Electronics. While there are controversies about who invented what, there is universal agreement that the ENIAC (Electronic Numerical Integrator And Computer) was the watershed project that showed electronic computing was possible. It was a masterpiece of electrical engineering, with unprecedented reliability and speed. The two men most responsible for its success were J. Presper Eckert and John W. Mauchly.
I recorded two days of interviews with "Pres" Eckert in 1989. He was 70 years old. My father was Pres' best friend from childhood and I'd spent my childhood playing with his children. I visited him regularly as an adult. On that day, we spoke in his living room in Gladwyne, Pa. -- most of the time sitting on the floor. We stopped talking about computers only to fiddle with his Nova Chord electronic organ, which predated ENIAC, and we fiddled with stereo speakers. On a second occasion I recorded a conversation at his daughter's home in western Massachusetts. Eckert died in 1995. I've had the interview tapes for many years, but decided to transcribe them for ENIAC's 60th anniversary.

How did calculating machines work before ENIAC?
Well, a person with a paper and pencil can add two 10-digit numbers in about 10 seconds. With a hand calculator the time is down to 4 seconds. The Harvard Mark 1 was the last of the electromechanical computers -- it could add two 10-digit numbers in 0.3 seconds, about 30 times faster than paper and pencil.
When I was a graduate student, the Moore School of Electronics had two analyzers that were essentially copies of Vannevar Bush's machine from MIT.
What could that machine do?
It could solve linear differential equations, but only linear equations. It had a long framework divided into sections with a couple dozen shafts buried through it. You could put different gears on the shafts using screwdrivers and hammers and it had "integrators," that gave [the] product of two shafts coming in on a third shaft coming out. By picking the right gear ratio you should get the right constants in the equation. We used published tables to pick the gear ratios to get whatever number you wanted. The limit on accuracy of this machine was the slippage of the mechanical wheels on the integrator.
That made me say, "Let's built electronic integrators and stick them into this machine instead of those wheel

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